The above-named professional personnel propose to collaborate with other members of the Children's Cancer Study Group A as well as with other members of other cooperative cancer study groups, in research on leukemia, malignant solid tumors and closely related disorders in children. The chief purpose of this study group is to cooperate in research on malignant diseases in children and, in particular, to study factors which may cause or influence cancer and to develop, evaluate and improve methods of diagnosis and treatment of malignant diseases in children.